The NCTM's Standards suggests that technology can be used as a tool to collect data, formulate conjectures, and engage in complex problems with messy numbers.

GeoGebra

Interactivity

• Make a Flake - snowflake maker with a virtual scissors
  
• Geometry 3-D Shapes (Annenberg)
• Building Big Shapes Lab - geometry that makes buildings strong
  
• Transformation Golf (Maths Online UK) - coordinate graphing
  
• National Library of Virtual Manipulatives (also available in Spanish)
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  Virtual Manipulatives Survey
  

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• Wolfram Demonstrations Project -sophisticated interactivity for MS and HS

• Tessellation Demo - make a translation tessellation with an index card "virtually"
  
• Jim McNeill Gallery - an artist to inspire MS kids!
  
• Shodor - Tessellate! - "deform" triangles, rectangles and squares and tessellate with a click
  
• Symmetry and Tessellations - author and mathematician Jill Britton's collection
• Jill's Tessellated Polyhedra patterns to print and assemble - great inspiration
• Symmetry in Hmong Textiles
• Native American Geometry
• Symmetry in Native American Pottery
  

You-Tube & Online Video Resources - geometry you have to see to believe! (includes templates for constructions)